The present invention relates to an apparatus for feeding semiconductor substrates (hereinafter referred to as wafers), or any other thin sheets or plates, such as printed circuit boards and printing plates, to a processing section, and moving the same therefrom to the next process. More particularly, the present invention relates to an apparatus for such use, wherein the apparatus is adapted for use in association with a heating medium, whereby the objects are heated and dried.
To feed wafers to a heat treating unit and transfer the same to the next step, there have been many proposals, among which are a pneumatic system (Japanese Patent Application Laid-Open No. 58-21332), a belt conveyor system (Japanese Utility Model Application Laid-Open No. 56-89251, Patent Application Laid-Open No. 58-223340, and Utility Model Application No. 57-97915), and a so called link-motion conveyor system (Japanese Patent Application Laid-Open No. 57-136336), which are discussed in detail below.
The pneumatic system, which transfers wafers by means of substantially upward air-blow, has a drawback that the wafers are apt to be stained with dirt flown by the air. In particular, when highly integrated circuits are included in the wafers, the problem of dirt becomes fatal to the quality control of the semiconductor products.
The belt conveyor system, which ordinarily uses a pair of conveyor belts to convey the wafers, employs air suction to hold the wafers on the finely finished surface of a hot plate. But, the wafers tend to adhere to the hot plate even after the suction is turned off because the wafers are also very smooth. Also, molten photoresist film which may protrude from the periphery of the wafer tends to stick to the hot plate. Each of these problems often causes the wafers to become dislocated from their required position on the conveyor belts.
To solve the problems of the belt conveyor system, it has been proposed that air be blown against the bottom surface of the wafers through the same pores or tubes used for suction purposes. However, this creates the dirt and dislocation problems previously mentioned.
The so-called link-motion or walking beam conveyor system has the advantage of positively lifting the wafers from the hot plate. However, the apparatus employed in these systems require a relatively large space in front and in back of the hot plate to allow the beam to move in its rectangular path. This disadvantage is especially troublesome for those factories of wafer manufacturers where sanitary conditions are strictly regulated, since it is desirable to minimize the size of the equipment as much as possible. Wafers of increased size, which are now in demand, make this problem even more troublesome. The foregoing problem makes the link-motion conveyor system objectionable.
The present invention is directed toward solving the aforementioned problems of conventional wafer conveyor systems. Specifically, it is a primary object of this invention to provide a system of feeding wafers for heat treatment, such that each wafer is lifted from the hot plate and thereafter immediately moved, so as to avoid possible dislocation of the wafer, and so as to secure smooth, trouble-free feeding of the wafers in an automatic sequence.
Another object of the present invention is to provide a system of feeding wafers for heat treatment in a minimum of space.
A further object of the present invention is to provide a wafer conveying system capable of securing operational safety and reliability.
Other objects and advantages of the present invention will become apparent from the detailed description hereinafter taken in conjunction with the accompanying drawings.